1. Field of the Invention
This invention relates to an electronic musical instrument of simplified construction. More particularly, it relates to such a musical instrument which may be provided in a single, easily portable package. Most especially, it relates to such a musical instrument which is suitable both for playing musical compositions in different scales and for demonstrating and teaching basic musical concepts.
2. Description of the Prior Art
There are a wide variety of electronic musical instruments which are commercially available, including, for example, electronic organs and synthesizers. As originally developed, such electronic musical instruments relied primarily on analog circuitry and separate oscillators for the notes generated in their operation.
Subsequently, digital circuitry for generation of musical tones was developed. A typical digital frequency generation circuit comprises an oscillator, e.g., a quartz crystal, which generates a frequency higher than that of any musical tone to be produced using the circuit. A plurality of frequency divider circuits then divides the oscillator frequency in order to provide the notes of a musical scale. For example, the commercially available MM 5891 MOS Top Octave Frequency Generator Integrated Circuit obtainable from National Semiconductor Corporation, Santa Clara, California is typical of such a prior art frequency generation circuit in which a fully parallel frequency division network provides the notes of the conventional chromatic scale. U.S. Pat. No. 3,590,131 describes another example of a frequency divider network for obtaining chromatic scales. While such circuits have proved to be highly suitable for generating notes of the chromatic scale, they are limited to that scale. While most music of western cultures is composed in the chromatic scale, most non-western music is composed in other scales, usually one or another diatonic scale.
In addition to being limited to the chromatic scale, such fully parallel frequency divider networks as the MM 5891 utilize more circuit elements than would be required with a frequency generator network that was not fully parallel. Since integrated circuit designers continually attempt to provide either more function in a given area or a given function in a smaller area, a need remains for the development of frequency generator networks which utilize a lesser number of circuit elements than the commercially available fully parallel frequency generators.
The design and implementation of prior art electronic musical instruments has further tended to make them sufficiently complex that they are too cumbersome for ready portability. This consideration provides further impetus for the development of an improved electronic musical instrument with increased portability. Just as the development of easily portable calculators has expanded the use of electronic computation, the provision of a truly portable electronic musical instrument capable of generating a wide variety of pleasing musical sounds should expand the utilization of electronic music.